Combustion pre-chamber assemblies for an internal combustion engine

ABSTRACT

A combustion pre-chamber assembly includes pre-chamber device body defining an annular plenum that is in fluid communication with the at least one bore that extends through the spark plug shell. The annular plenum is also in communication with at least one purging passage that extends from the annular plenum to an end surface of the pre-chamber device body. Residual exhaust gases in the annular volume of the spark plug are purged by fresh charge flow from the main combustion chamber as the piston approaches top dead center. The fresh charge flow that is provided to the annular plenum through the at least one purging passage and into the annular volume of the spark plug through the at least one bore through the spark plug shell.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT Application No.PCT/US18/32696, filed May 15, 2018, which claims the benefit of thefiling date of U.S. Provisional Application No. 62/506,179 filed on May15, 2017, each of which is incorporated herein by reference.

TECHNICAL FIELD

The subject matter of this application relates generally to internalcombustion engines, and more specifically to spark plugs and combustionpre-chambers used in fuel ignition systems of internal combustionengines.

BACKGROUND

Spark plugs having adaptations for use with pre-chamber assemblies areknown, as shown in, for example, U.S. Pat. No. 9,225,151 issued Dec. 29,2015, incorporated by reference herein in its entirety.

It is well documented that the use of combustion pre-chamber deviceswith spark plugs, such as shown in FIG. 1, in pre-chamber assemblies ina spark ignited, natural gas fueled, engine can result in an extendedlambda (air/fuel ratio) range. Generally this allows the engine to beoperated leaner than an open chamber system, resulting in lower NOxemissions while maintaining good cycle-to-cycle peak cylinder pressurevariation. With these engines there is usually an operational trade-offbetween NOx emissions and fuel consumption. For applications that havehigher NOx emissions requirements than others, better fuel consumptioncan be obtained by running the pre-chamber engine slightly richer (i.e.,at a lower lambda value). Depending on the cost of fuel, this operationat a lower lambda value can offer substantial savings to the engineowner/operator.

Spark plugs are used in conjunction with various types of combustionchamber configurations to initiate a flame in a flammable fuel and airmixture. Some combustion chamber configurations include passivepre-chamber, open chamber, and fuel fed pre-chamber configurations.Pre-chambers are useful for initiating and propagating the combustionflame for pre-mixed gaseous-fueled engines. In particular, pre-chambersprovide benefits as applied in lean-burn natural gas engines which canbe difficult to ignite using conventional open chamber typeconfigurations.

Passive pre-chambers include a combustion volume in which the spark plugis located. The combustion volume of the pre-chamber is linked to themain combustion chamber of the cylinder by the use of orifices ornozzles. The spark plugs include a central cathode electrode and one ormore outer ground or anode electrodes, which at least partially surroundthe cathode electrode to create a gap therebetween. The spark pluginitiates a combustion event by generating a spark (e.g., an electroncurrent) that spans the gap between the central cathode electrode andone or more outer ground electrodes. More specifically, the sparkinitiates a flame that propagates through the pre-chamber volume. Thiscombustion creates a sudden increase in pressure in the pre-chambercreating a large pressure difference across the orifices between thepre-chamber and main chamber. The pressure difference forces the flameto propel through the orifices into the main combustion chamberresulting in a successful combustion event.

After a successful combustion event, the residual exhaust gases in themain chamber are scavenged during the exhaust stroke of the pistonwithin the cylinder. During the intake stroke, a fresh, pre-mixed airand fuel mixture (charge) is pulled into the main cylinder via anexpansion event driven by the piston. However, some residual exhaustgases in the passive pre-chamber volume and between the spark plugelectrodes are not completely scavenged and remain within thepre-chamber during the exhaust and intake strokes. During the subsequentcompression stroke, the pressure difference between the main chamber andpre-chamber increases, forcing a fresh charge through the orifices intothe pre-chamber, which compresses the residual exhaust gases towards thebackside of the pre-chamber where the spark plug is located. Theresidual exhaust gases trapped in the area toward the back side of thepre-chamber, on the side opposite to the main chamber, can lead topre-ignition and/or abnormal combustion, especially when the engine isoperating at richer lambda (air/fuel ratio) ranges.

Engine testing and analysis by the inventors have discovered that theresidual gas trapped in the annular volume around the spark pluginsulator nose is not readily purged in subsequent combustion cycles andas a result can be heated to a temperature sufficient to causepre-ignition. This was found to be the case particularly when the engineis operated at richer lambda values. Output from fluid dynamics analysesshows low velocity in the spark plug annular volume nearest to theinsulator nose at the rearmost portion of the pre-chamber volume. Outputfrom CO₂ concentration analyses in a spark plug indicates evidence ofunacceptably high levels of CO₂ residual gas remaining in the spark plugannular volume, particularly in zones near the base of the insulatornose. Output from temperature analyses measuring temperatures withinvarious zones of the spark plug annular volume indicates evidence ofhigh gas temperatures in the spark plug annular volume, especially nearthe base of the insulator nose, as a result of the lack of mixing orpurging of the residual gas from the spark plug annular volume.

Improvements are needed in spark plugs and/or pre-chamber devices toimprove the purging of the residual gases in the annular spark plugvolume and pre-chamber volume, thus extending the lambda operating rangewithin which the engine may be advantageously operated.

SUMMARY

The subject matter of the present application has been developed inresponse to the present state of the art, and in particular, in responseto the problems and needs in the spark plug and combustion pre-chamberart that have not yet been fully solved by currently availablecombustion pre-chamber and spark plug designs.

According to one embodiment as described herein, a spark plug designedfor use in a combustion pre-chamber assembly in a lean-burn, gaseousfueled, internal combustion engine includes at least one bore extendingthrough a shell of a spark plug positioned to form a passageway betweenan annular volume around the spark plug insulator nose and a pre-chambervolume of a pre-chamber device, thus directing a purge of exhaust gasestrapped in the annular volume to a space formed by the exterior of thespark plug body and the interior of the pre-chamber device.

In another embodiment, the combustion pre-chamber assembly includes apre-chamber body for connection with a spark plug. The pre-chamber bodydefines an annular plenum that is in fluid communication with the atleast one bore that extends through the spark plug shell. The annularplenum is also in communication with at least one purging passage thatextends from the annular plenum to an end surface of the pre-chamberbody that is located at the combustion chamber. Residual exhaust gasesin the annular volume of the spark plug are purged by fresh charge flowfrom the main combustion chamber as the piston approaches top deadcenter. The fresh charge flow that is provided to the annular plenumthrough the at least one purging passage and into the annular volume ofthe spark plug through the at least one bore through the spark plugshell.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

In order that the advantages of the subject matter may be more readilyunderstood, a more particular description of the subject matter brieflydescribed above will be rendered by reference to certain embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the subject matter and arenot therefore to be considered to be limiting of its scope, the subjectmatter will be described and explained with additional specificity anddetail through the use of the drawings, in which:

FIG. 1 is a cross-sectional side view of a typical pre-chamber assemblyinstalled in a cylinder head;

FIG. 2 is a cross-sectional side view of an electrode end portion of aspark plug of an embodiment;

FIG. 3 is another cross-sectional side view of an electrode end portionof a spark plug of an embodiment;

FIG. 4 is an end elevation view of an electrode end of a spark plug ofan embodiment;

FIG. 5 is an end elevation view of an electrode end of a spark plug ofan embodiment having a swirl feature;

FIG. 6 is another end elevation view of an electrode end of a spark plugof an embodiment having a swirl feature;

FIG. 7 is a cross-sectional side view of an electrode end portion of aspark plug of an embodiment having bores of smaller diameter; and

FIG. 8 is an end elevation view of an electrode end of a spark plug ofan embodiment having bores of a smaller diameter.

FIG. 9 is a schematic side section view of a combustion pre-chamberassembly in which any of the spark plug embodiments of FIGS. 2-8 can becoupled with a pre-chamber device having an annular plenum and purgingpassages to facilitate removal of residual gases.

FIG. 10 is a schematic perspective view of the combustion pre-chamberassembly of FIG. 9.

DETAILED DESCRIPTION

There is disclosed herein an improved spark plug design to allow forimproved flow of fresh charge into the annular volume around the sparkplug insulator. In addition, there is disclosed herein an improvedpre-chamber device for use with the improved spark plug that facilitiespurging of the residual exhaust gasses. The improvements result inimproved flow of fresh charge mix into the annular volume around thespark plug insulator, which dilutes or purges the residual gasses thatare present from the previous cycle and delaying the onset ofpre-ignition. The improvements have the effects of lowering the gastemperature in the annular volume, thus making the spark plug moreresistant to pre-ignition and/or abnormal combustion. The improvementsalso result in extension of lambda (air/fuel ratio) operating range ofengine, the pre-chamber, and/or the spark plug as used therein.

FIG. 1 shows a cross-sectional side view of an example prior art passivepre-chamber assembly mounted directly to the cylinder head 200 of aninternal combustion engine. The cylinder head 200 of conventionalinternal combustion engines includes a plurality of spark plug recesses202 for receiving a spark plug 10. Typically, the conventional sparkplug is fitted within a respective recess 202 such that all or part ofthe cathode and anode electrodes at the electrode end portion 12 of theconventional spark plug are positioned within (e.g., directly exposedto) a respective main combustion chamber 402 of the engine or cylinderblock when the cylinder head 200 is mounted to the cylinder liner 400that is supported in the engine block. The recess 202 is fluidly coupledto an air-fuel mixture inlet for receiving an air-fuel mixture from airintake and fuel sources (not shown).

As shown in FIG. 1, a conventional spark plug may be connected with apassive pre-chamber device 100, which is fitted within the spark plugrecess 202. The pre-chamber device 100 includes a body 105 that definesa pre-chamber volume 115. The pre-chamber volume 115 effectivelyspatially separates the spark plug (e.g., spark plug 10) from the maincombustion chamber 402. The body 105 includes one or more orifices ornozzles in its distal end wall that fluidly connect the pre-chambervolume 115 with the main combustion chamber 402. As discussed above, thepre-chamber volume 115 facilitates the initiation and propagation of acombustion flame for the internal combustion engine. The body 105 mayinclude connectors (e.g., external threads) matching or similar indimensions the connectors (e.g., external threads) that are found onconventional spark plugs. The connectors of the body 105 mate withcorresponding connectors (e.g., internal threads) formed within thespark plug recess 202 to secure the pre-chamber device 100 to thecylinder head 200. The body 105 includes a receptacle 107 configured toreceive and retain a spark plug 10 within the body 105 such that thecathode and anode electrodes of the spark plug 10 are positioned withinthe pre-chamber volume 115.

The body 105 includes pre-chamber inlet apertures for receiving theair-fuel mixture from the inlet of the cylinder head 200 into thepre-chamber volume 115. The pre-chamber volume 115 is in fluidcommunication with a gap 117 which is in the form of an annular spacebetween the exterior surface of the spark plug 10 and the inner surfaceof the pre-chamber volume 115, the gap 117 being positioned toward aproximal portion of an electrode end portion of the spark plug 10.

FIG. 2 is a cross-sectional side view of an electrode end portion 12′ ofa spark plug 10′ according to the present disclosure which is modifiedfrom the prior art spark plug 10. The spark plug 10′ according to oneembodiment includes an outer ground electrode portion 14 with aplurality of outer ground electrodes 16. The outer ground electrodes 16can be defined as outer anodes or anode electrodes. Further, the sparkplug 10′ includes a central cathode electrode 18 about which the outerground electrodes 16 are positioned at a distal end 19 of the spark plug10′.

Generally, the outer electrodes 16 at least partially laterally surroundor are positioned laterally about the central electrode 18. In otherwords, the outer electrodes 16 are radially outwardly spaced-apart fromthe central electrode 18, defining a space or gap between the centralcathode electrode 18 and the outer electrodes 16. The outer electrodes16 extend from a proximal portion to the distal end 19 of the spark plug10′, adjacent a head 20 of the central electrode 18. In certainimplementations, the outer electrodes 16 are angled radially inwardlytoward a central longitudinal axis A of the spark plug 10′ in a proximalto distal direction as shown in FIG. 2. In certain implementations, theouter electrodes 16 each include an aperture 22 that facilitates theflow of fresh charge and exhaust gas into and out of the space definedbetween the central cathode electrode 18 and the outer electrodes 16.

The spark plug 10′ includes an outer shell 24 that surrounds the body ofthe spark plug 10′, formed generally in a cylindrical shape at aproximal portion of the electrode end portion 14 of the spark plug 10′as shown in FIG. 2. The shell 24 ends at the proximal portion of theelectrode end portion 14 such that the ground electrodes 16 are open tothe pre-chamber volume 115. The spark plug 10′ further includes aninsulator including an insulator nose 26. The insulator nose 26surrounds the central electrode 18 and generally is formed in the shapeof a hollow tube surrounding the central electrode 18 and positioned tobe concentric to the cylindrical shape of the body of the centralelectrode 18.

The inner surfaces of the preceding structures form a space within thespark plug 10′ that is generally annular in shape. Specifically, asshown in FIG. 2, inner surface 16 a of the ground electrodes 16, innersurface 24 a of the shell 24, surface 26 a of the insulator nose 26, andsurface 18 a of the central electrode 18 together form a boundary aroundan interior annular volume 28 formed around insulator nose 26 inside theelectrode end portion 12′ of the spark plug 10′. The gap 28 includes afront gap portion 28 a formed near the distal end 19 of the spark plug10′. The gap 28 further includes a rear gap portion 28 b formed near theproximal portion of the electrode end portion 12′ of the spark plug 10′.The rear gap portion 28 b forms an annular space surrounding theproximal portion of the insulator nose 26.

Although the spark plug 10′ illustrated herein includes a circularcentral electrode and a plurality of spaced-apart concentric outerelectrodes, in some embodiments, the spark plugs can include differentshaped central electrodes with fewer or more than the depicted number ofouter electrodes. Also, the outer electrodes may be formed in a numberof different known shapes. For example, in one embodiment, a spark plugincludes a single outer electrode that surrounds the central electrode,and in another embodiment a spark plug includes a single square centralelectrode with four concentric outer electrodes.

As shown in the spark plug 10′ in FIG. 2, in an embodiment, an aperturein the form of bore 30 such as a drilled hole is formed in the shell 24.In an embodiment, the bore 30 is in the form of a hollow,cylindrically-shaped aperture formed in the shell 24 by drilling. Thebore 30 extends in a direction that is at an oblique angle relative tothe central longitudinal axis A of the spark plug 10′. The bore 30extends between an inner end 32 of the bore 30, positioned along theinner surface 24 a of the shell 24, and an outer end 34 of the bore 30,positioned along the outer surface 24 b of the shell 24.

The angle at which the bore 30 extends relative to the centrallongitudinal axis A may vary as appropriate to the geometric shape ofthe spark plug 10′ in the region of the insulator nose 26. In anembodiment as depicted in FIG. 3, the bore 30 extends in a directionwherein a central longitudinal axis B of the bore 30 is at an obliqueangle θ relative to the direction of the central longitudinal axis A.The extension of the bore 30 in the oblique angular direction directsmovement of exhaust gases trapped in the annular region 28 b and/orannular volume 28 toward the gap 117. Formed to extend at such anoblique angle θ, the bore 30 forms a passageway directed so as to aidthe expulsion of the exhaust gasses trapped in the annular region 28 band/or annular volume 28 outwardly through the bore 30 into the gap 117,and in turn, into the pre-chamber volume 115 to which the gap 117 is influid connection.

As seen in FIGS. 2 and 3, in an embodiment, the inner end 32 of the bore30 is located at a position that is at a greater distance from thedistal end 19 of the spark plug 10′ than the position of the outer end34 of the bore 30. In an embodiment, the inner end 32 of the bore 30 islocated at a position such that the distance between the inner end 32and the distal end 19 of the spark plug 10′ is greater than the distancebetween the distal end 26 b of the insulator nose 26 and the distal end19 of the spark plug 10′. In such manner, the inner end 32 is positionedto aid the expulsion of the exhaust gases left over from the previouscombustion event out of the rearmost portion of the annular region 28 boutwardly through the bore 30 into the gap 117. In such a position, theinner end 32 is positioned to aid such purge of exhaust gases in amanner that is not accomplished by prior art features such as apertures22 formed in ground electrodes 16, which are not positioned in therearmost portion of the annular region 28 b, as may be seen from theconfiguration shown in FIG. 2. In this manner, the annular region 28 band the adjacent annular volume 28 are substantially purged of residualexhaust gas and the region 28 b and annular volume 28 are moreeffectively replenished with fresh air/fuel mixture at the time of sparkignition (e.g., generally between 20-degrees and 16-degrees before topdead center (BTDC).

FIG. 4 is an end elevation view taken from the side of the distal end 19of a spark plug 10′ of one embodiment. Outer ends 34 of a plurality ofthe bores 30 (six bores 30, as depicted in FIG. 4) are formed in theouter surface 24 b of shell 24. Bores 30 diverge from one another in thedistal direction toward distal end 19.

FIG. 5 is an end elevation view taken from the side of the distal end 19of another embodiment spark plug 10″ similar to spark plug 10′ exceptthe bores 30″ in spark plug 10″ are formed at a tangential angle toimpart a swirl characteristic to exhaust gases exiting the bores 30″through outer ends 34″. For example, line D represents the longitudinalaxis of the bore 30″ having the outer end 34″ depicted in FIG. 5. Thelongitudinal axis D extends in a direction tangential to a point on thecircumference of a circle defined by head 20, where the circle lies in aplane C and has a center point on central longitudinal axis A, and theplane C is perpendicular to the central longitudinal axis A of the sparkplug (see FIG. 3). Therefore, the bores 30″ do not intersectlongitudinal axis A. That is to say, the exhaust gases exiting bores 30″through outer end 34″ will be directed in a tangential or swirlingdirection with respect to central longitudinal axis A. In this manner, aswirl characteristic is imparted to the exiting gases as they enter intoand circulate within gap 117 and pre-chamber volume 115. The swirl maybe imparted at different radial angles with respect to centrallongitudinal axis A. The swirl may be imparted in counterclockwiseand/or clockwise directions.

As shown in FIG. 6, in another embodiment the angle of longitudinal axisD′ may be selected such that the exhaust gases exiting bore 30″ throughouter end 34″ will be directed in a tangential direction with respect tocentral longitudinal axis A, so as to be directed toward an aperture 22in an adjacent ground electrode 16. This feature may aid circulation ofexhaust gases in the front gap portion 28 a of gap 28. The configurationof FIG. 6 also shows an embodiment having a larger number of bores 30″as compared to the configuration of FIG. 5, i.e. eight bores versus sixbores.

The diameters of the bores 30 may vary in accord with the configurationof the spark plug 10′, 10″ in question and the operating conditions forwhich it is developed. For example, FIG. 7 shows a cross-sectional sideview of an electrode end portion 12′ of a spark plug 10′, 10″ that issimilar in general to the configuration shown in FIG. 2, except that thebores 30 of the FIG. 7 configuration have smaller diameters than thebores depicted in FIG. 2. FIG. 8 shows an end view of the distal end 19of a spark plug 10′, 10″ of an embodiment wherein the bores 30 areformed with smaller diameters such as shown as in the configuration ofFIG. 7.

Applying the configurations shown in FIGS. 2-8, the bores 30, 30″ arepositioned to communicate between the rear portion of the annular volume28 so that fresh air/fuel charge present at the outer ends 34, 34″ ofthe bores 30, 30″ enters the outer ends 34, 34″ and flows through thebores 30, 30″, resulting in dilution and/or purging of the residualcharge from the annular volume 28 around the spark plug insulator nose26. This dilution and/or purging effectively lowers the gas temperaturein the annular volume, thus preventing pre-ignition and/or abnormalcombustion. As exemplified in the drawing figures, the numbers of anddiameters of the bores 30, 30″ may be adjusted to produce the desiredperformance results. The range of lambda values at which the engine maybe operated increases, with less instances of pre-ignition and/orabnormal combustion. The passages may be placed at an angle so as toinduce some amount of clockwise or counterclockwise swirl in gasesexiting either of the ends of the bores 30, 30″.

Referring now to FIGS. 9 and 10, a further improvement in the combustionpre-chamber devices assembly is shown with respect to a combustionpre-chamber assembly 500. The combustion pre-chamber assembly 500includes a spark plug such as any of the spark plugs 10′, 10″ describedabove with respect to FIGS. 2-8. In the illustrated embodiment of FIGS.9-10, spark plug 10′ is used with the description below, but is notlimited to spark plug 10′.

Pre-chamber assembly 500 includes a pre-chamber device 502 connected tothe spark plug 10′. The pre-chamber device 502 includes a body 504defining a pre-chamber volume 515 and at least one nozzle 510 extendingthrough a distal end 506 of the body 504 for communication with acombustion chamber 402 of the internal combustion engine. The body 504of the pre-chamber device 502 further defines an annular plenum 508 incommunication with one or more, or all, of the bores 30 of the sparkplug 10′. The body 504 of the pre-chamber device 502 further includes atleast one passage 512 extending between and opening at the annularplenum 508 and the distal end 506 of the body 504. In the embodimentillustrated in FIG. 10, the body 504 is hidden with the annular plenum508 is shown in solid lines along with bores 30 and passages 512 tobetter illustrate the arrangement therebetween.

The annular plenum 508 is formed as a groove in an inner wall surface516 of body 504 that is continuous and extends completely around body504 in the illustrated embodiment. In other embodiments, plenum 508 isnot continuous but is arranged to provide a connection for each of thebores 30 with at least one of the passages 512. Passages 512 extend fromthe groove forming annular plenum 508 through body 502 and open at thedistal end 506 of body 504 in communication with combustion chamber 402.Bores 30 from the spark plug 10′ are also in communication with annularplenum 508 when spark plug 10′ is connected to the pre-chamber device502. In the illustrated embodiment, bores 30 are greater in number thanpassages 512. In one embodiment, twice as many bores 30 are providedthan passages 512 to facilitate flow from annular volume 28. In otherembodiments, the same or lesser number of bores 30 may be provided ascompared to passages 512.

In operation, the annular volume 28 of the spark plug 10′ receivescharge flow from the combustion chamber 402 of the cylinder through thepassages 512, the annular plenum 508 and the bores 30. In particular, asthe piston in combustion chamber 402 moves from bottom-dead-center (BDC)to top-dead-center (TDC) on the compression stroke, the pressure risesin the main combustion chamber 402 of the cylinder. Due to the area ofthe openings of pre-chamber device nozzles 510 and the area of theopenings of passages 510 relative to the pre-chamber volume 515, theflow of fresh charge into the pre-chamber volume 515 from combustionchamber 402 is restricted, resulting in a pressure differential betweencombustion chamber 402 and pre-chamber volume 515. This pressuredifferential increases as the piston approaches TDC. This pressuredifferential causes fresh charge to flow from combustion chamber 402through passages 510 and annular plenum 508.

As the pressure rises in annular plenum 508, fresh charge begins to flowthrough the bores 30 of the spark plug 10′ and into the annular volume28 around the hot insulator nose 26. The fresh charge mixes with anddisplaces hot residual gases that are present in the spark plug annularvolume from the previous cycle. The cool fresh charge suppressespre-ignition from occurring in the annular volume around the hot sparkplug insulator 26. Once the properly timed spark occurs, combustionproceeds within the pre-chamber volume 515, which causes the pressure inthe pre-chamber volume 515 to rise above the pressure in the combustionchamber 402. The hot combustion products are then expelled from thepre-chamber volume 515 through the restrictive pre-chamber nozzles 510and through the passages 510 to combustion chamber 402. This results ina very high energy ignition source for the charge in combustion chamber402.

As is evident from the figures and text presented above, a variety ofaspects of the present disclosure are contemplated.

In one aspect, a combustion pre-chamber assembly includes a spark plugfor an internal combustion engine that includes an insulator nose and ashell around the insulator nose, the spark plug further including anannular volume between the shell and the insulator nose, and at leastone bore that extends through the insulator shell from the annularvolume. The combustion pre-chamber assembly also includes a pre-chamberdevice connected to the spark plug. The pre-chamber device includes abody defining a pre-chamber volume and at least one nozzle extendingthrough a distal end of the body for communication with a combustionchamber of a cylinder of the internal combustion engine. The body of thepre-chamber device further defines an annular plenum in communicationwith at least one bore and also includes at least one passage extendingbetween and opening at the annular plenum and the distal end of thebody.

In one embodiment, the at least one bore includes a plurality of bores,and/or the at least one passage includes a plurality of passages. Inanother embodiment, the annular volume of the spark plug receives chargeflow from the combustion chamber of the cylinder through the at leastone passage, the annular plenum and the at least one bore.

In another embodiment, the spark plug includes a distal end with acenter cathode electrode and at least one ground electrode, and theinsulator nose extends around a proximal end of the center cathodeelectrode and has a distal end. The bore includes an inner endpositioned on an inner side of the shell in communication with theannular volume. In a refinement of this embodiment, the inner end of thebore is positioned such that a distance between the inner end of thebore and the distal end of the spark plug is greater than a distancebetween the distal end of the insulator nose and the distal end of thespark plug.

In yet another embodiment, the at least one bore includes a first numberof bores positioned around the insulator shell. In a refinement of thisembodiment, the at least one passage includes a second number ofpassages positioned around the body of the pre-chamber device. In afurther refinement, the first number is greater than the second number.In another embodiment, the body of the pre-chamber device includes aninner surface around the pre-chamber volume and the annular plenum is agroove in the inner surface that extends around the pre-chamber volume.

According to another aspect, a combustion pre-chamber assembly includesa spark plug for an internal combustion engine. The spark plug includesan insulator nose and a shell around the insulator nose, and an annularvolume between the shell and the insulator nose. The at least one boreextends through the insulator shell from the annular volume. Theassembly also includes a pre-chamber device for connection to the sparkplug. The pre-chamber device includes a body defining a pre-chambervolume and at least one nozzle extending through a distal end of thebody for communication with a combustion chamber of a cylinder of theinternal combustion engine. The body of the pre-chamber device furtherhas a groove that forms an annular plenum and the at least one bore ofthe spark plug opens into the annular plenum. The body of thepre-chamber device further includes at least one passage extendingbetween and opening at the annular plenum and the distal end of thebody. The at least one passage, the annular plenum, and the at least onebore provide for fluid flow between a main combustion chamber of theinternal combustion engine and the annular volume of the spark plug.

In one embodiment, the at least one bore includes a first number ofbores positioned around the insulator shell. In a refinement of thisembodiment, the at least passage includes a second number of passagespositioned around the body of the pre-chamber device. In a furtherrefinement, the first number is greater than the second number. Inanother embodiment, the at least one nozzle includes a plurality ofnozzles extending through the distal end wall of the body of thepre-chamber device.

According to another aspect, a combustion pre-chamber device includes abody defining a pre-chamber volume opening at a proximal end of the bodyand at least one nozzle extending through a distal end of the body forproviding fluid flow between the pre-chamber volume and a combustionchamber of an internal combustion engine. The proximal end of the bodyis configured for connection with a spark plug. The body of thepre-chamber device further includes a groove that forms an annularplenum around the pre-chamber volume. The body of the pre-chamber devicealso includes at least one passage extending between and opening at theannular plenum and the distal end of the body. The at least one passageand the annular plenum provide for fluid flow through the body betweenthe combustion chamber of the internal combustion engine and the annularplenum at the proximal end of the body.

In one embodiment, the at least one chamber includes a plurality ofchambers. In another embodiment, the at least one nozzle includes aplurality of nozzles. In still another embodiment, the groove is locatedon an inner surface of the body that extends around a proximal end ofthe pre-chamber volume. In another embodiment, the groove is continuous.

According to another aspect, a combustion pre-chamber device is providedfor connection with a spark plug. The pre-chamber device includes a bodydefining a pre-chamber volume and at least one nozzle extending througha distal end of the body for communication with a combustion chamber ofa cylinder of the internal combustion engine. The body of thepre-chamber device further defines an annular plenum in communicationwith at least one bore and also includes at least one passage extendingbetween and opening at the annular plenum and the distal end of thebody.

In another aspect, an apparatus is described in the nature of a sparkplug for an internal combustion engine. The spark plug includes a distalend with a center cathode electrode and at least one ground electrode,an insulator nose formed around a proximal end of the center cathodeelectrode and having a distal end, a shell formed around a body of thespark plug, and a bore formed in the shell. The bore comprises an innerend positioned on an inner side of the shell, and the inner end ispositioned such that a distance between the inner end and the distal endof the spark plug is greater than a distance between the distal end ofthe insulator nose and the distal end of the spark plug.

In a further aspect, a method includes providing a spark ignition engineincluding a pre-combustion assembly including a first end defining aninner passage to receive a spark plug, and a second end defining apre-combustion chamber, and installing in the inner passage a spark plugand combustion pre-chamber as described above.

In yet another aspect, a method includes operating a spark ignitionengine including a pre-combustion assembly including a first enddefining an inner passage to receive a spark plug, and a second enddefining a pre-combustion chamber, and a spark plug as described aboveand a combustion pre-chamber as described above.

In the above description, certain relative terms may be used such as“up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,”“right,” and the like. These terms are used, where applicable, toprovide some clarity of description when dealing with relativerelationships. But, these terms are not intended to imply absoluterelationships, positions, and/or orientations. For example, with respectto an object, an “upper” surface can become a “lower” surface simply byturning the object over. Nevertheless, it is still the same object.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment. Similarly, the use of theterm “implementation” means an implementation having a particularfeature, structure, or characteristic described in connection with oneor more embodiments of the present disclosure, however, absent anexpress correlation to indicate otherwise, an implementation may beassociated with one or more embodiments.

The described features, structures, advantages, and/or characteristicsof the subject matter of the present disclosure may be combined in anysuitable manner in one or more embodiments and/or implementations. Inthe following description, numerous specific details are provided toimpart a thorough understanding of embodiments of the subject matter ofthe present disclosure. One skilled in the relevant art will recognizethat the subject matter of the present disclosure may be practicedwithout one or more of the specific features, details, components,materials, and/or methods of a particular embodiment or implementation.In some instances, the benefit of simplicity may provide operational andeconomic benefits and exclusion of certain elements described herein iscontemplated as within the scope of the invention herein by theinventors to achieve such benefits. In other instances, additionalfeatures and advantages may be recognized in certain embodiments and/orimplementations that may not be present in all embodiments orimplementations. Further, in some instances, well-known structures,materials, or operations are not shown or described in detail to avoidobscuring aspects of the subject matter of the present disclosure. Thefeatures and advantages of the subject matter of the present disclosurewill become more fully apparent from the following description andappended claims, or may be learned by the practice of the subject matteras set forth hereinafter.

The present subject matter may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A combustion pre-chamber assembly, comprising: aspark plug for an internal combustion engine that includes an insulatornose and a shell around the insulator nose, the spark plug furtherincluding an annular volume between the shell and the insulator nose,and at least one bore that extends through the insulator shell from theannular volume; and a pre-chamber device connected to the spark plug,the pre-chamber device including a body defining a pre-chamber volumeand at least one nozzle extending through a distal end of the body forcommunication with a combustion chamber of a cylinder of the internalcombustion engine, the body of the pre-chamber device further definingan annular plenum in communication with at least one bore, the body ofthe pre-chamber device further including at least one passage extendingbetween and opening at the annular plenum and the distal end of thebody.
 2. The combustion pre-chamber assembly of claim 1, wherein the atleast one bore includes a plurality of bores.
 3. The combustionpre-chamber assembly of claim 2, wherein the at least one passageincludes a plurality of passages.
 4. The combustion pre-chamber assemblyof claim 1, wherein the annular volume of the spark plug receives chargeflow from the combustion chamber of the cylinder through the at leastone passage, the annular plenum and the at least one bore.
 5. Thecombustion pre-chamber assembly of claim 1, wherein the spark plugincludes: a distal end comprising a center cathode electrode and atleast one ground electrode; the insulator nose extends around a proximalend of the center cathode electrode and has a distal end; and the borecomprises an inner end positioned on an inner side of the shell incommunication with the annular volume.
 6. The combustion pre-chamberassembly of claim 5, wherein the inner end of the bore is positionedsuch that a distance between the inner end of the bore and the distalend of the spark plug is greater than a distance between the distal endof the insulator nose and the distal end of the spark plug.
 7. Thecombustion pre-chamber assembly of claim 1, wherein the at least onebore includes a first number of bores positioned around the insulatorshell.
 8. The combustion pre-chamber assembly of claim 7, wherein the atleast one passage includes a second number of passages positioned aroundthe body of the pre-chamber device.
 9. The combustion pre-chamberassembly of claim 8, wherein the first number is greater than the secondnumber.
 10. The combustion pre-chamber assembly of claim 1, wherein thebody of the pre-chamber device includes an inner surface around thepre-chamber volume and the annular plenum is a groove in the innersurface that extends around the pre-chamber volume.
 11. A combustionpre-chamber assembly, comprising: a spark plug for an internalcombustion engine that includes an insulator nose and a shell around theinsulator nose, the spark plug further including an annular volumebetween the shell and the insulator nose, and at least one bore thatextends through the insulator shell from the annular volume; and apre-chamber device for connection to the spark plug, the pre-chamberdevice including a body defining a pre-chamber volume and at least onenozzle extending through a distal end of the body for communication witha combustion chamber of a cylinder of the internal combustion engine,the body of the pre-chamber device further having a groove that forms anannular plenum and the at least one bore of the spark plug opens intothe annular plenum, the body of the pre-chamber device further includingat least one passage extending between and opening at the annular plenumand the distal end of the body, the at least one passage, the annularplenum, and the at least one bore providing for fluid flow between amain combustion chamber of the internal combustion engine and theannular volume of the spark plug.
 12. The combustion pre-chamberassembly of claim 11, wherein the at least one bore includes a firstnumber of bores positioned around the insulator shell.
 13. Thecombustion pre-chamber assembly of claim 12, wherein the at leastpassage includes a second number of passages positioned around the bodyof the pre-chamber device.
 14. The combustion pre-chamber assembly ofclaim 13, wherein the first number is greater than the second number.15. The combustion pre-chamber assembly of claim 11, wherein the atleast one nozzle includes a plurality of nozzles extending through thedistal end wall of the body of the pre-chamber device.
 16. A combustionpre-chamber device, comprising: a body defining a pre-chamber volumeopening at a proximal end of the body and at least one nozzle extendingthrough a distal end of the body for providing fluid flow between thepre-chamber volume and a combustion chamber of an internal combustionengine, the proximal end of the body being configured for connectionwith a spark plug, wherein the body of the pre-chamber device furtherincludes a groove that forms an annular plenum around the pre-chambervolume, the body of the pre-chamber device further including at leastone passage extending between and opening at the annular plenum and thedistal end of the body, the at least one passage and the annular plenumproviding for fluid flow through the body between the combustion chamberof the internal combustion engine and the annular plenum at the proximalend of the body.
 17. The combustion pre-chamber device of claim 16,wherein the at least one chamber includes a plurality of chambers. 18.The combustion pre-chamber device of claim 16, wherein the at least onenozzle includes a plurality of nozzles.
 19. The combustion pre-chamberdevice of claim 16, wherein the groove is located on an inner surface ofthe body that extends around a proximal end of the pre-chamber volume.20. The combustion pre-chamber device of claim 16, wherein the groove iscontinuous.